Apparatus for treating steel melts



F` HARDERS 3,02 7,150

APPARATUS FOR TREATING STEEL MELTS Filed March 4, 1959 March 27, 1962.-v F. HARDERS 3,027,150

APPARATUS FOR TREATING STEEL MELTS Filed March 4, 1959 2 sheets-sheet 2 i i i MAQ/V /NVENTOR United States Patent Cfiice 3,027,150 Patented Mar. 27, 1962 3,027,150 i, APPARATUS FOR TREATING STEEL MELTS Fritz Harders, Burenbruch, Post Ergste, uber Schwerte (Ruhr), Germany, assigner to Dortmund-Hrder Httenunion Aktiengesellschaft, Dortmund, Germany Filed Mar. 4, 1959, Ser. No. 797,063

Claims priority, application Germany Mar'. 10, 1958 3 Claims. (Cl. 266--34) The invention relates to rau apparatus for degasifying metal, e.g. steel melts, and in particular to an apparatus of this kind which is of simple construction, so that it can quite' easily be incorporated in any steel works. The invention'mainly relates to the construction of the vacuum chamber of the degasifying apparatus.

The degasifying apparatus to which the invention relates comprises a heated `vacuum chamber and a vessel, e.g.y a ladle,v which is disposed underneath the vacuum chamber and which is charged with'the metal to be degasitied and into which dips a short pipe extending from the bottom of the vacuum chamber. `With thisdegasify ing apparatus the steel melt may be treated in the following manner:

Only a portion of the melt is periodically introduced each time into the vacuum chamber through the pipe in the bottom of the vacuum chamber, where it is degasilied and then returned through this -pipe into the ladle underneath the vacuum chamber. The steel is introduced into the vacuum chamber and discharged again from it simply by varying the depth of immersion of the pipe inthe steel melt, the latter being raised or lowered accordingly for this purpose. This cycle of operations is repeated until the steel which is to be degasied has acquired the desired degree of purity.

The usefulness of the above described degasifying process depends mainly on the construction of the vacuum vessel, which is heated in known manner. The known vacuum vessels are round or rectangular in cross-section. Their heating devices are disposed at the least possible distance above the liquid level of the melt being degasiiied. In this form of construction of the vacuum vessels, the heating bodies are worn away much too rapidly by the metal being degasified, which bubbles while it is being degasilied, and sprays against the heating bodies, so that these are soon eroded away and dissolved.

When the heating rods or electrodes are arranged as in the known vacuum chambers, near the liquid level of the metal being degasified, the refractorylining above the steel melt is insuciently heated. The metal, which is at a high temperature and bubbles up in the vacuum vessel and gets broken up into droplets, then solidies on the cool parts of the refractory lining of the vacuum vessel and forms deposits there, which after only a short time occupy most of the free space above the level of the liquid.

These difficulties are now overcome, by the invention, by making theV vacuum chamber pear shaped. The lower part of the chamber, from which the short pipes extend, lead off, is thus in the form of a broad-based pan-like vessel. The metal in this pan-like part presents a large surface to the vacuum, which, as is known, is particularly advantageous for the degasifying process.

In vertical cross-section the vacuum chamber gradually narrows down towards its arched roof, so that the chamber is pear-shaped. In the upper part, i.e. where the cross-section of the chamber is smallest, is tted theV heating device, consisting of a carbon rod or electrodes. The arrangement of the heating device in this position causes intensive heating of the upper part of the chamber and its lining, s o that the danger of forming deposits is excluded. At the Sametime, the dis! tance of the heating device from the level of the molten metal is so great that the heating elements are now not damaged by metal spray. The pear-like shape of the chamber owing to the constant reduction of its crosssection and its pan-shaped lower part, results in considerably less loss by radiation. The heating device can therefore be arranged at a lgreater distance from the liquid level than previously.

Some constructional embodiments of degasifying apparatus according to the invention are illustrated, diagrammatically and by way of example in vertical section in the accompanying drawings, in which:

` FIGURE l shows a vacuum vessel according to the invention and FIGURE'Z illustrates the vacuum chamber together with the other apparatus of the degasifying plant.

Referring to the drawings, the vacuum chamber 1 is pear-shaped. Thus the lower part is in the form of a broad-based pan 2, in which the metal 3 presents a large surface area 4 to the vacuum. Above this pan 2 the cross-section of the vacuum chamber gets progressively smaller until it reaches the space 5 which contains the heating device consisting of a carbon rod 6. The refractory wall 7 of the vacuum chamber is surrounded by a vacuum-tight steel jacket 8. A short pipe 9 extends downwards from the bottom of the chamber. It consists of a steel pipe 10 which is lined with refractory material 11.

At the top, the vacuum chamber is covered by an arched roof 12. .Around this arch, at some distance from it, there is a hood 13 vacuum-tightly connected to the steel jacket 8 and having an attachment 14. The vacuum chamber 1 is connected to a vacuum pumping plant 23 (FIGURE 2) through an opening 15 in the arched roof and a pipe 15' connected to the hood 13. Treatment materials can be charged from a charging device 16 through an opening 17 in the arch 12 of the chamber into the melt in the vacuum chamber 1. In the cylindrical attachment 14 to the hood 13 of the arch, there is provided an auxiliary arch 18 which is particularly well insulated and reduces the radiation losses from the main arch, and in particular from its opening 15.

Owing to the pear-shaped form of the'vacuum cham ber the radiating surface above the metal 3 which is to be degasied is considerably reduced and the refractory lining of the upper part of the chamber is strongly heated, so that no deposits are formed by metal which is sprayed onto refractory lining.

FIGURE 2 shows an apparatus which is operated discontinuously, i.e. in batches, and has only one pipe 9 opening into the bottom of the vacuum chamber and dipping into a ladle 19. The ladle 19 is mounted on the platform 20 of a truck 21. lt can be raised together with the platform by a hydraulic lifting device 22.. When it is raised, a portion of the melt in the ladle 19 is introduced into the vacuum vessel. When the ladle is lowered the degasified metal ows back into the melt in the ladle.

The vacuum chamber is fixed in position and the vacuum pumping plant 23 is arranged on a stage 24.

I claim:

1. In apparatus for degassing molten metal, comprising a refractory lined vessel defining a chamber, means for evacuating said chamber to produce a partial vacuum therein, a container for said molten metal disposed below said chamber, a pipe affixed to the bottom of said vessel and opening into the lower Vend of said chamber,

refractory lining of .said chamber being pear-shaped wherein the lower portion 'thereof is formed as a rela` tively shallow hearth adapted to hold the molten metal in a shallow pool having a relatively large surface area, the sidewalls of 'said lining sloping lgradually upwardly to terminate in a relatively narrow upper end, carbon rod heating means extending horizontally `across said chamber adjacent the upper end of said sidewalls, said lining also including an arched roof of refractory material mounted on the upper end of said sidewalls and above saidV heating element, ysaid arched roof reflecting the heatrfrom said element to the -rnelt in the lower end of said vessel,-said sloping sidewalls facilitating conduction of said heat from said element to `the melt, 'and` a vacuum-tight hood surrounding said arched roof, said vacuum-tight hood and Vsaid arched roof each 'having apertures therein vfor placing -said chamber in communication with said vpartial vacuum producing means.

2. The apparatus recited in claim l wherein said isidewalls terminate at their upper ends in a short cylindrical section and wherein said heating fe'lemen't s disposed in said cylindrical section, said device also including means for charging said vacuum chamber with treatment materials, and wherein said hood and said arched roof each have a second aperture formed therein for placing said 4 chamber in communication with said last-mentioned means.

3. The device set forth in claim 2 wherein said vacuum-tight hood is spaced from said arched roof and an auxiliary arch is disposed between said arched roof and said hood and over the rst of said apertures in said roof to reflect heat escaping through said apertures b'ack into said chamber. Y

References Cited in the le of this patent Jour. vof Metals, pp. 742- 3, June l1'95'6. 

